Conventional systems for inspecting display panels include the system described in Cummins, R. et al, "Evaluating image quality and defect characterization in flat panel display", Photon Dynamics, Inc., 1504 McCarthy Blvd., Milpitas, Calif., USA.
In conventional display panel inspection, an image of a display panel, including a multiplicity of pixels, is imaged by a sensor which is also pixelated, the pixels of the sensor normally not being contiguous (i.e., having a fill factor of less than 100%) and normally not being equally sized nor perfectly aligned relative to the pixels of the display panel image.
FIG. BA-1 is a diagram of a display panel image including, for simplicity, four display panel pixels 10 which are imaged by a sensor including, for simplicity, six sensing elements 20. The sensor is ideal, i.e. theoretical, in the sense that the sensor elements thereof are contiguous. Typically, nonuniform display panel intensity shows up as a local variation in the video signal of the sensors. The numbers within the display panel pixels 10 indicate the proportion of the total area of the display panel pixel that is sensed by the respective camera pixel, in arbitrary units.
FIG. BA-2 is a diagram of a display panel image which is not ideal in that the sensor elements 20 are not contiguous. In FIG. BA-2, for simplicity, three display panel pixels 30, 40 and 50 are shown. The portion of display panel pixel 40 which is not sensed, as indicated by cross-hatching 70 is smaller than the portions of display panels 30 and 50, as indicated by diagonal lines 80. This results in inaccuracies in measuring the intensities of the display panel pixels. Specifically, local variation in the video signal of the sensors does not necessarily indicate nonuniform display panel intensity.